keypress_for_input_type_of_number.js

// Requires the following attributes be set: step, min, and max on the input
			input_number: function() {
			  if (!$('input[type=number]').length) {
			    return;
			  }
			  
			  function getStep(el) {
	        return parseInt($(el).attr('step')) || 1;
			  }
			  
			  function stepUp(el) {
	        var step = getStep(el);
	        var max = parseInt($(el).attr('max'));
	        var val = parseInt($(el).val());
	        
	        val = val + step;
	        
	        if (val <= max) {
  		      if (el.stepUp) {
  		        el.stepUp(step);
  		      }
  		      else {
		          // there is a max value set
		          if (val != max) {
		            val = val + step;
		            if (val > max) {
		              val = max; // if the increase is greater than max, then set to max so that we don't go over
		            }
		          }
		        
  		        $(el).val(val);
  		      }
	        }
			  }
			  
			  function stepDown(el) {
	        var step = getStep(el);
	        var min = parseInt($(el).attr('min'));
	        var val = parseInt($(el).val());
	        
	        val = val - step;
	        
	        if (val >= min) {
  		      if (el.stepDown) {
  		        el.stepDown(step);
  		      }
  		      else {
		          // there is a max value set
		          if (val != min) {
		            val = val - step;
		            if (val < min) {
		              val = min; // if the decrease is less than min, then set to min so that we don't go under
		            }
		          }
		        
  		        $(el).val(val);
  		      }
	        }
			  }
			  
			  function isNumber(obj) {
           return (obj === +obj) || (obj.toString() === '[object Number]');
			  }
			  			  
			  $('input[type=number]').keydown(function(ev){
			    if (isNumber(parseInt(this.value))) {
  			    var keyCode = ev.keyCode;
  			    if (keyCode == '38') {
  			      // up arrow
  			      stepUp(this);
  			    }
  			    else if (keyCode == '40') {
  			      // down arrow
  			      stepDown(this);
  			    }
		      }
			  });
			}